Apparatus for making glass film



1945. e. SLAYTER ETAL 2,386,511

APPARATUS FOR MAKING GLASS FILM Filed oct. 2, 1943 s Sheets-Sheet 1 GamaSlayler Henry Snow INVENTORS 9,1945. 5; SLAVY'TER ETAL' "2,386,511

APPARATUS FOR MAKING, GLASS FILM Filed Oct. 2, 1943 5 Sheets-Sheet 2-Gamea 5,15 ,Zer 1' fienr'ysnew a INVENTORS ATTDRNEYS Oct. 9, 1945. I s.SLAYTER E TVAL 2,386,511

APPARATUS FOR MAKING GLASSFILM Filed Oct 2, 1945 5 sheets-sheet 3 Ga m4.Silciy ler j Henry Snow IN V EN TORS M ii '- J ATTORNEYS:

' appreciable size.

Patented Oct." 9, 1945 A UNlTED STATES PATENT OFFICE 2,336,511 APPARATUSFOR MAKING GLASS FILM Games Slayter and Henry Snow, Newark, Ohio,

assignors to Owens-Corning Fiberglas Corporation, Toledo, Ohio, acorporation of Delaware Application October 2,1943, Serial No. 504.786

' Claims.

I This invention relates to an improved appara tus for manufacturingglass film.

' There are numerous and diversified uses for glass film produced inaccordance with this invention. However, for the purpose of thisdescription, it will suflice to point out that the product resultingfrom the use of the apparatus claimed herein is not only capable "ofreplacing.

. mica' in practically all of its numerous applications but, inaddition, possesses the advantage that it may be fashioned inpractically any size sheet, as distinguished from mica sheets which arenecessarily formed of a multitude of relatively small flakes.

With the above in view, the present invention has as one of its objectsthe manufacture of relatively wide thinsheets of glass on a productionbasis. g

Heretofore it has been extremely difficult to produce glass in very thinsheets or flakes of any One prior attempt to obtain such glass waseffected by blowing a large glass bubble until it broke or fractured.This produced.

"fragments of unusually small size,a great many of which were slightlywedge-shaped due to the conditions attendant, the blowing of the bubble.More recent methods of producing foliated glass consist in flowingordrawing glass in the form of a thin .walled tube or cylinder which isafterward .broken into small pieces; In a, previous attempt to produce athin sheet of glass ,within the range of .0001 to .0005 inch inthickness a continuous strip or ribbon was employed. It. was found thatas the stream issued from the melter bushing it had atendency to neck intoapproximately twothirds of its former width and as it was attenuatedat high speed a substantial bead formed along each edge. This, ofcourse, proved undesirable andv was due mainly to'the efiect of surfacetension on the glass of the extreme thinness of the attenuated ribbon.

It is another object of the invention to form sheets of thin glasswithout marginal beads by flowing molten glass in the form of a tubularstream and attenuating it to a film-like thickness.

In attempting to flatten tubes formed in the above manner to obtain flatsheets or ribbons therefrom,- the walls at the point of folding orcreasing become hardened or set before theypan be brought entirelytogether and thus form a holby the attenuating rolls. This greatlyreduces the available flat width of the sheet or ribbon I throughoutwhich the thickness is substantially uniform within normal commerciallimits. It is another object of the invention to form a thin walled tubeof glass which may be attenuated and flattened into a ribbon of uniformthickness and of any desired practical width and length.

It sometimes occurs in flattening a tube of the above character by meansof rolls or other attenuating means that wrinkles are formed in theplane surface. This results in an'undesirable' condition by producing awall having an uneven surface and varying thickness and it is a furtherobject of the invention to form a ribbon of glass having plane surfaceswhich are free of wrinkles and other blemishes.

A further feature of this invention is to partially flatten a tubularstream of glass before it is introduced to the attenuating means and 1tion of the glass during the final flattening operation bytheattenuating means is reduced and breakage of the ribbon is avoided.

A still further object of this invention is to urge and maintain thewalls of the stream toward the inner surfaces of the tube by introducing pressure therein as the stream passes through the tube. Thus thewalls of the stream are held against collapsing while in a plasticstate.

A still further object of the invention is the formation of alaminatedribbon of glass which is accomplished by forming a' thin walledtube of glass, flattening the tube to form a double ply ribbon, andintroducing a bonding agent into i the tube before it is flattened.

In practicing'the present invention it has been found that the adjacentthin waiE of the ribbon low edge which shatters as the ribbon is engagedhave a tendency to abrade each other when the ribbon is rolled orcoiled. .It is an object of this invention to alleviate this conditionby applying a lubricating agent to the interior surface of the Walls ofthe tube as the tube is attenuatedto prevent self-abrasion duringsubsequent handling. thereof.

The foregoing, as well as other objects, will be made more apparent asthis description proing and attenuating device M. 7

any tendency to over stress the hollow glass stream ceeds especiallywhen considered inconnection with the accompanying drawings wherein:

Figure 11 is a diagrammatic sectional view of one type of apparatusfound satisfactory for manufacturing glass film;

Figure 2 is a fragmentary semi-diagrammatic sectional view of theapparatus taken at right angles to the showingin Figure 1;

Figure 3 is a front elevational -view of the bushing employed forflowing molten glass in the form of a' hollowstream; Figure 5 is abottom plane view of the bushing shown in Figure 3;

Figures 5 and 6 illustrate a modified form of the bushing which may beemployed in practicing the present invention; Figure 5 being a. per-.spective view of the bushing from beneath, and Figure 6 a fragmentarybottom plan view showing the discharge orifices. I

Briefly described, glass of a specified formula is introduced'into abushingl0 and is melted in the bushing by the application of sufilcientheat to impart the desired flow characteristics to the glass. bushing intheform of a hollow stream II and The molten glass is discharged fromthe the drawings is formed of a materialhaving good electrical as wellas heat conducting characteristics and comprises a container portion I!open at the top to enable glass batch briquettes or marbles to bereadily introduced into the bushings. In the present instance thecontents of the bushing is heated to-the desired temperature by passingan electric current through the bushing and for this purpose a pair orterminal lugs I8 are respectively integrally joined-to opposite sides ofthe container portion ll of the bushing. As shown particularly inFigures 1 and 3, the

container portion ll of the bushing is provided the latter is'introducedinto the ,upper end of a vertical tube i2 having the lower or deliveryend portion l3 flattened to correspondingly flatten the stream I I. Inthis connection it will be noted that the glass stream is internallysupported and maintained in contact with the inner surface of the tubel2 by introducing fluid under pressure into the upper end of the hollowstream.

As the flattened stream discharges from the delivery end l3 .of the tubel2 it is introduced to a combined attenuating and flattening device l4.

shown in Figure 1 as comprising apair of rolls I5. The rolls iii arerespectively supported at opposite sides of the path of travel of thestream in close proximity to each other and are opera-' tively connectedto suitable driving mechanism '(not' shown) for-relatively high speedrotation in opposite directions toward each other. The rolls 15 are of alength somewhat greater than the width of the delivery end of the tubeI2 and not only further flatten the stream II to form a wide very thinribbon of glass but also exert a pulling force on the ribbon in adownward direction to attenuate the stream.

The stretching of the thin walls of the tubular stream as the shape ischanged from cylindrical at the bushing orifice to the elongated andflattened conformation adjacent the attenuating rolls sometimes causeswrinkles to be formed along the edges. This is an unsatisfactorycondition due to 'the tendency of the wrinkles .to extend well into thesurface of v,the ribbon and thus produce a film having an uneven"surface and varying in thickness beyond the practical limits oftolerance. By employing thetubev l2 it has been found that thesedifficulties are substantially reduced, thus increasing the usable Ioutput of film and limiting the wasteaccordsly.

It follows from the above that the hollow stream .ofglass H is partiallyflattened at a gradual rate by the tube I2 prior to entering the finalflatten- This minimizes and avoids fracturing the stream by thecooperating rolls l5. In .this manner it is possible to produce acontinuous very thin glass ribbon of substantial width which may becollected or packaged on a rotating spool l6. i i

The bushing In shown in the several figures of with baffles l9 arrangedto compel the glass to travel along a circuitous passage asit passesdown through the container portion. Actually the glass is compelled to'take a zigzag course from one side of the bushing to the other duringits flow to the bottom or discharge end of the bushing. .Thus, thebattles l9 retard the flow of glass throughthe heat zone or containerportion I! of the bushing and also compelthe glass to flow in heatconducting relation to the container walls during passage of the glassto the vquired homogeneity and viscosity or flow characportion-11 in theform of streams. The heatand viscosity of the glass is adjusted so thatthe streams fiowing'from the orifices 22 thoroughly wet the: innersurface of the tubular discharge wall 20 below the plate 2i and unitetoform the tubular glass stream ll.

As the glass stream H flows from the discharge wall 20 of the bushingitenters the vertical tube l2 and is progressively flattened by thedelivery end portion iii of the tube so that the peripheral dimension atthe flattened endiremains substantially equal to the circumference ofthe discharge wall. As previously stated, the glass stream ii isinternally supported and maintained adjacent the inner surface of thevertical tube i2 by introducing fluid under pressure into the upper endof the tubular stream. In the present instance,

air under sufllcient pressure to accomplish the above is dischargedthrough a centrally arranged opening formed in the plate 2| by a conduit23. The conduit 23 is shown. in Figure 2 as extending from the plate 2|thf'oughone side of the bushinglto a suitable source .of supply notshown here- ,in. In actual practicerit has, been found that an airpressure slightly greater than the pressure of the surroundingatmosphere is sufflcient 'to prevent collapsing of the stream' and tomaintain I the walls of the latter in contact with the flattening tubel2.

As the flattened stream ll flows from the delivery end of the tube l2,it passes between the rolls l5 which are respectively supported atopposite sides of the path of travel of the stream for rotation inopposite directions. The rolls are driven at a relatively high rate ofspeed by mechanism not shown herein and not only exert a downward pullon the stream to attenuate-the 2,sse,s11 3 latter but, in addition,further flatten the stream cements the opposed surfaces together, andproduces a laminated product of increased strength which canbe cut to adesign much in the manner of a sheet of mica. vThe bonded ribbon furtheris more resistant to damage incurred in handling and subsequentoperations than ribbons of unbonded ty-pe. j

When it is desired to produce the flim ribbon and employ only singlethicknesses thereof, no bond material is applied and at such times thereis a tendency of the opposed walls to abrade each other duringsubsequent handling, tending to weaken the walls and cause fracturesthereof.

To overcome this it is possible to introduce a lubricant into the tubeas it is formed. The lubricant prevents such abrasion and insures a moreuniform product. Such lubricant may be castor oil,vegetable oil or alight mineral oil.

As the relativel wide glass ribbon passes from between the attenuatingrolls l5, it may be coliected in any one of a number of different ways.

In Figure 2 of the drawings, the ribbon is shown as packaged on asuitable spool I8 which is driven at a high rate of speed b any suitablemechanism not shown herein. A. lubricating .medium, such aslow-viscosity mineral oil or the like, is preferably applied to theribbon of glass by a spray or sprays 25 supported between theattenuating rolls I8 and the packaging spool l6. This arrangementreduces the abrasive action of contacting the glass surfaces as theribbon is coiled or rolled and tends to minimize breakage thereof.

While the present invention is primarily conoerned with the productionof film glass in continuous ribbon form, the ribbon may be broken by anysuitable means to produce flakes ofsubstantially any desired size.

-The embodiment of the invention shown in Figures 5 and 8 differs fromthe construction previously described in that the discharge area II ofthe bushing 29 is an elongated ring having round ends and discharges acorrespondingly shaped glass stream. ,With this arrangement.

theglass-streamispartialiyflattened atthebushing thus reducing theflattening action of the attentuating rolls to a minium as the ribbon isformed. Further b reasonoi the oval shape of the stream the shaping tubeI: may be eliminated in this form of the invention sincethestreammorenearlyapproximatestheflnal shape. Also, a lubricating orbonding medium may be employed as previously described;

We claim:

1. Apparatus'for producing glass mm comprising a bushing having anannular discharge orifice through which molten glass flows in the formof a hollow stream, means for introducing fluid under pressure into thestream, and means for confining the stream including a tube positionedto receive the stream and having a portion which progressively flattensto correspondingly flatten the stream.

2. Apparatus for producing a thin glass ribbon comprising a bushinghaving an annular discharge orifice through which molten glass flows inthe form of a hollow stream, means for introducing fluid under pressureinto the stream,

a tube supported beneath the bushing in a position to receive the streamas it is discharged from the bushing and shaped at its lower endtoflatten the stream to a width greater than the diameter at the dischargeorifice, and means at the discharge end of the tube for attenuating thestream to form a thin flat ribbon 'ofglass. 3. Apparatus for producing athin glass ribbon having means for flowing glass into the form of ahollow stream, a tube positioned to receive the hollow stream and havinga flattened portionat the discharge end thereof, and means Y 'forintroducing fluid into the stream under sufflcient pressure to maintainthe walls of the glass stream into contact with the inner surface of thetube and thereby correspondingly flatten the stream.

4. Apparatus for producing glass fllm comprising a bushing having anannular discharge oriflce through which molten glass flows in the formof a hollow stream, an elongated tube positioned with the receiving endadjacent the bush ing oriflce to receive the glass stream flowing fromthe orifice and having the delivery end flattened, means for introducingfluid into the stream under sufllcient pressure to maintain the walls ofthe stream into contact with theinner surface of the tube, and meanssupported at the delivery end of the tube for attenuating and furtherflattening the stream to form a thin flat ribbon of glass. v

5. An apparatus for producing glass fllm in ribbon form comprising abushing having an elongated discharge" oriflce through which moltenglass flows in the form of a hollow partially flattened stream, a tubearranged adjacent said oriflce and adapted to receive the stream flowingtherefrom, said tube having its lower end shaped to further: flatten thestream, means for introducing air under pressure into the stream tomaintain the wall thereof. in contact with the wall of said tube, andattenuating means ad- Jaoent the lower end of the tube for attenuatingthe flattened stream to a ribbon.

. HENRY SNOW.

